﻿I.AMPSILIS 41 



cosus with a rather strongly developed posterior ridge. He 

 has only the type in his collection and I have never seen any- 

 thing like it elsewhere. 



Var. satura (Lea). 



A form rather common in southwestern waters. It is greatly 

 inflated, with livid or smoky-colored, sometimes blackish 

 epidermis, and the marsupial sv/elling is remarkably developed. 

 It gradiially merges into the type. 



Southwestern States to Sabine River, Texas. 



Type locality, Alexandria ; Lake Calcashue, New Orleans, La. 

 Unio satur Lka, Pr. Am. Phil. Soc, V., 1852, p. 252; Tr. Am. 



Phil. Soc, X, 1852, p. 205, pi. XVII, fig. 19: Obs., V, 1852. 



p. 21, pi. XVII, fig. 19.— Chenu, Man., 1859, II, p. 138. fig. 



666.— SowERBY, Conch. Icon., XVI, 1868, pi. xcii, fig. 501. 

 Margaron (Unio) satur Lea, Syn.. 1852, p. 24; 1870, p. 37. 

 Lampsilis rentricosus var. satur Simpson. Syn., 1890, p. 527. 



Var. lurida n. v. 



Throughout the St. Lawrence drainage a form is found, 

 which is generally less inflated than the type, having lurid, ash- 

 colored or smoky epidermis, which is lighter colored on the 

 posterior ridge. This form is generally believed to be Idea's 

 Unio canadensis and is rayless or feebly rayed, but it is really 

 quite diflferent from the specimen to which the great author 

 gave that name. The form, which I call lurida, rarely has rays 

 and when they are present they are dark smoky-brown. The 

 typical ventricosa occurs more or less abundantly throughout 

 the St. Lawrence area. 



Lampsiijs excavata (Lea). 



Shell inflated, subsolid, the male irregularly ovate or rhom- 

 boid, the female obovate, with a high, decided posterior ridge ; 

 beaks high and full; ligament large, brown, extending for- 

 ward in a narrow excavation in front of the beaks ; epidermis 

 smooth and shining on the disk, roughened and wrinkled on 

 the somewhat truncated post-slope, tawny or greenish-yellow, 

 showing a few green rays; hinge line with a slight double 



